1. Field of the Invention
This invention relates to an endoscope apparatus which can measure the spatial characteristics such as length, area, shape, and so on, of a photographic object.
2. Description of the Related Art
A stereo optical adapter through which images of an object of interest are taken is attached at a tip of an endoscope to form an endoscope apparatus which can measure various spatial characteristics of the object by the principle of triangulation (stereo measurement). Such an apparatus is widely used. (See, for example, JP 2004-33487A.) The stereo optical adapter may be, for example, a direct-view optical adapter or a side-view optical adapter.
FIG. 6 shows a side-view type stereo optical adapter attached to the tip portion of the endoscope. FIG. 7 is a cross-sectional view of the tip portion of the endoscope taken along line VII-VII of FIG. 6. As shown in FIGS. 6 and 7, a side-view stereo optical adapter 7 is attached to the tip portion 21 of the endoscope by a securing ring 50 by screwing a female screw 50a of the securing ring 50 on a male screw 21a of the endoscope tip portion 21. As shown in FIG. 6, a pair of optical lenses 56 and 57 and two objective lens systems 58 and 59 are formed in the tip portion of the side-view stereo optical adapter 7. As shown in FIG. 7, a prism 49a and an optical lens 49b which bend an optical axis 90 degrees are provided directly below the two objective lens systems 58 and 59. A view mask 55b which has two quadrilateral (for example) openings 55d (see FIG. 8) is arranged at the end face side (nearer to the tip portion 21 of the endoscope) of the optical lens 49b as shown in FIG. 7. On an imaging side of the solid-state image sensor 2a arranged in the endoscope tip portion 21, two optical images which have passed through the openings 55d of the view mask 55b are imaged to be observed as shown in FIG. 9. As shown in FIG. 9, when a photographic object 30 (object of interest), which is the character F in FIG. 6, is imaged, the side-view stereo optical adapter provides mirrored images 30aL and 30aR of the photographic object 30 due to the action of the prism 49b. Since the mirrored images may not be suitable for observation, the mirrored images of the photographic object may be horizontally inverted to be observed as erect images 30bL and 30bR, as shown in FIG. 10. Alternatively, a vertically inverted or rotated image may be suitable for observation depending on the action of the prism, and an enlarged or reduced image may be suitable depending on a size of the object of interest.
In order to perform stereo measurement by triangulation using the images obtained from two viewpoints as mentioned above, optical data including the optical characteristics of an optical system, such as the focal length of two or more optical systems, etc., is required. For this reason, the optical data has to be generated by measurement. See, for example, JP2004-49638A, the entire contents of which are incorporated herein by reference.